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Free calculator

Use this calculator to

  • Convert metered kWh into kilograms and tonnes of CO2
  • Annualise a daily, weekly or monthly consumption figure
  • Compare grid intensity options, including a custom factor for your supply
  • Estimate tree-planting and car-distance equivalents for internal reporting

Electricity Carbon Footprint Calculator

Calculate the carbon footprint (kg CO₂e) of your electricity use based on UK grid intensity.

kWh
CO₂ Emissions

Formulas

  • CO₂ (kg) = kWh × grid intensity (kg/kWh)
  • UK grid 2026 (DESNZ): ~131 gCO₂/kWh (0.131 kg/kWh)
  • Trees to offset: 1 tree ≈ absorbs ~21 kg CO₂/year
  • Equivalent miles driven: 1 km by car ≈ 170 gCO₂

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Common scenarios

Select one to run it in the calculator above.

For business

Why this matters for businesses

SECR, CSRD and Scope 2 reporting all start with kWh and end with tCO2e. Both ends depend on the right grid intensity factor for the right reporting year, the right methodology (location-based versus market-based), and a defensible source for every line item across every meter. The calculation looks straightforward until the auditor asks for the working file, which is usually when the assumptions stop holding up and the report goes back for a rewrite.

Market-based reporting against a REGO-backed or PPA-backed supply contract can move the reported Scope 2 figure materially, and that delta matters for B-Corp recertification, customer ESG questionnaires, and increasingly for bank covenants and large-customer supplier qualification packs. A 10 GWh-per-year business reporting against a residual UK grid factor versus a renewable supply contract is the difference between roughly 1,800 tCO2e and close to zero in the market-based figure, which is the kind of swing investors notice.

Purely Energy is B-Corp certified and runs Purely Insights to consolidate HH and NHH consumption across every supplier into one source of truth, with location-based and market-based Scope 2 reporting built in alongside the spend data. When a finance team needs the carbon figure to stand up alongside the spend figure in the same dashboard, with traceable line-item sources, that is the system we will deploy alongside the procurement contract.

Common questions

How do I calculate the carbon footprint of my electricity?

Multiply the kWh consumed by a grid carbon intensity factor expressed in kg CO2 per kWh. For UK reporting, use the UK Government conversion factor for the reporting year, which is published annually for exactly this purpose; the factor falls over time as the grid decarbonises, so always match the factor to the year of consumption. The calculator also annualises daily, weekly or monthly meter readings before applying it.

Which grid intensity option should I choose?

For formal reporting, pick the option matching the UK Government conversion factor for your reporting year, or enter it through the custom field if your year is not listed. Comparisons across years should hold the factor constant so you measure consumption change rather than grid change. The EU average option suits sites on the continent, and the custom field handles supplier-specific or international factors.

What is the difference between location-based and market-based emissions?

Location-based reporting applies the average grid factor for your region to every kWh, regardless of tariff. Market-based reporting reflects your contracts: electricity backed by REGOs (Renewable Energy Guarantees of Origin) can be reported with a much lower, or zero, scope 2 figure. The GHG Protocol asks companies to disclose both, because a green tariff changes the market-based number while the physical grid mix sets the location-based one.

Does a renewable tariff make my electricity zero carbon?

For market-based scope 2 reporting, REGO-backed supply can be counted at zero emissions. Physically, the electrons you draw still come from the live grid mix, and even wind and solar carry small lifecycle emissions from manufacture and construction. Treat a renewable tariff as a reporting and procurement decision, and pair it with consumption reduction, since a kWh you never use is zero carbon under every methodology.

Do UK businesses have to report electricity emissions?

Quoted companies and large unquoted companies and LLPs fall under SECR (Streamlined Energy and Carbon Reporting), which requires annual disclosure of UK energy use and the associated emissions, calculated with the government conversion factors. Many smaller firms now report voluntarily because customers and lenders ask for the numbers in tenders and ESG questionnaires. Metered kWh from your bills is the starting point either way.

Related calculators

The conversions that procurement and engineering use alongside this one.